Glycated hemoglobin HbA1c

Glycated hemoglobin (HbA1c)

Measurement of glycated hemoglobin (HbA1c) is performed primarily to monitor diabetes treatment. Elevated HbA1c levels may indicate problems with blood glucose control, which can increase the risk of diabetes-related complications.

Diabetes is characterized by persistently elevated blood glucose levels. Treatment focuses on maintaining stable blood glucose levels, which helps slow the progression of the disease.

Untreated or poorly controlled diabetes can lead to serious complications, particularly nephropathy (kidney disease), retinopathy (damage to the retinal blood vessels), neuropathy and diabetic foot syndrome, erectile dysfunction, and cardiovascular diseases (including heart attack and stroke).

In people with diabetes, blood glucose levels should be measured several times a day; however, HbA1c testing allows for an assessment of long-term glycemic control (up to 3 months prior to the test).

Glycated hemoglobin – the test

Glycated hemoglobin is formed when hemoglobin binds with glucose. Hemoglobin, produced in red blood cells, transports oxygen from the lungs to all cells of the body and contains a small amount of bound glucose. Since red blood cells are permeable to glucose molecules, higher blood glucose levels (e.g., in patients with poorly controlled diabetes) intensify this process.
The HbA1c test determines the average amount of glucose bound to hemoglobin over the past 3 months (approximately 120 days, corresponding to the lifespan of a red blood cell). About half of the HbA1c value reflects glycemic control during the month preceding the test.

Glycated hemoglobin – when should the test be performed?

HbA1c testing is performed in the following situations:

• monitoring diabetes control,
• planning changes in treatment, e.g. initiating insulin therapy,
• screening for carbohydrate intolerance,
• newly diagnosed diabetes,
• monitoring diabetes in pregnant women,
• poor glycemic control (based on the patient’s self-monitoring results).

Patients with well-controlled diabetes (stable disease course) should have HbA1c measured once a year. In other cases (e.g., poorly controlled diabetes or after a change in treatment), more frequent testing is recommended – every 3 months.

Elevated hemoglobin

Elevated HbA1c values indicate poor diabetes control and may require modification of treatment. Increased HbA1c levels are also associated with a higher risk of developing diabetes-related complications. A correlation has been demonstrated between HbA1c levels and diabetic retinopathy (damage to the retinal blood vessels), which may even lead to vision loss. Maintaining HbA1c levels within the normal range reduces the risk of complications such as nephropathy, retinopathy, neuropathy, and cardiovascular disorders.

Currently, the Polish Diabetes Association (2018) does not recommend HbA1c testing for the diagnosis of diabetes.

Symptoms of elevated HbA1c levels

Increased HbA1c values most often indicate inadequate glycemic control. In such cases, characteristic symptoms may occur, including:

• excessive thirst,
• frequent urination,
• a feeling of dryness in the mouth,
• chronic fatigue and weakness,
• weight loss despite increased appetite (particularly typical of type 1 diabetes).

Glycated hemoglobin – preparation for the test

The test involves collecting a blood sample into an EDTA tube in accordance with standard blood collection procedures: skin disinfection, application of a tourniquet, and applying pressure to the puncture site after the procedure. The entire process takes a few minutes.

1. Blood collection itself takes approximately several to a dozen seconds.
2. Improper preparation for the test may result in a result that is not fully reliable.
3. Blood should be drawn in the morning hours.

HbA1c – preparation

• HbA1c testing does not require special preparation. The patient does not need to be fasting; however, it is recommended to avoid eating immediately before blood collection. Drinking a small amount of water in the morning is allowed.
• The test involves drawing blood from a vein, which is then sent to a laboratory for analysis.
• Blood collection should be performed in the morning hours.
• Before the test, the patient should remain at rest for 10–15 minutes (in a seated position).

HbA1c test results

• The test result is available within 3 working days.
• The result can be collected at the reception desk of any Center.

HbA1c reference values

The current treatment goal for diabetes is to keep HbA1c at or below 7.0% (53 mmol/mol). This target is general and should be individualized based on the patient’s clinical situation, especially in cases of type 1 diabetes, children and adolescents, people with recently diagnosed type 2 diabetes, patients with advanced disease accompanied by complications and/or comorbidities, women who are planning pregnancy or are already pregnant, as well as older adults. In such cases, the target HbA1c level may be higher or lower.

If abnormal results are obtained, consultation with a physician is recommended in order to discuss them in detail.

Factors that may affect the test result

• recent bleeding,
• hemolytic anemia,
• iron deficiency anemia.

Who should abnormal results be consulted with?

• Endocrinologist
• Internist
• Diabetologist